Synthesis and characterization of a polymetallic supermolecule containing four ruthenium(II)-bipyridine complexes attached to an iron(II) polyimine center

Toma, Henrique E.; Chavez-Gil, Tulio

doi:10.1016/s0020-1693(96)05475-8

Cited by 38 publications

(25 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Our laboratory has recently reported that cyclic voltammetry is one of the most sensitive evaluators of the electronic properties of aryl-substituted bis(imino)pyridines. 53,54,55 Reduction potentials between −2.35 and −2.83 V (vs Fc/Fc + ) were observed in THF solution depending on the specific substitution pattern of the bis(imino)pyridine. Performing identical measurements on the free bis(arylimidazol-2-ylidene)pyridine, iPr CNC, 56 in THF solution (1 mM iPr CNC in 0.1 M [ n Bu 4 ]PF 6 electrolyte) were unsuccessful as no reversible redox waves were observed, suggesting a less thermodynamically accessible radical anion for this ligand class.…”

Section: Resultsmentioning

confidence: 99%

Catalytic Hydrogenation Activity and Electronic Structure Determination of Bis(arylimidazol-2-ylidene)pyridine Cobalt Alkyl and Hydride Complexes

et al. 2013

View full text Add to dashboard Cite

The bis(arylimidazol-2-ylidene)pyridine cobalt methyl complex, (iPrCNC)CoCH3, was evaluated for the catalytic hydrogenation of alkenes. At 22 °C and 4 atm of H2 pressure, (iPrCNC)CoCH3 is an effective pre-catalyst for the hydrogenation of sterically hindered, unactivated alkenes such as trans-methylstilbene, 1-methyl-1-cyclohexene and 2,3-dimethyl-2-butene, representing one of the most active cobalt hydrogenation catalysts reported to date. Preparation of the cobalt hydride complex, (iPrCNC)CoH was accomplished by hydrogenation of (iPrCNC)CoCH3. Over the course of 3 hours at 22 °C, migration of the metal-hydride to the 4-position of the pyridine ring yielded (4-H2-iPrCNC)CoN2. Similar alkyl migration was observed upon treatment of (iPrCNC)CoH with 1,1-diphenylethylene. This reactivity raised the question as to whether this class of chelate is redoxactive, engaging in radical chemistry with the cobalt center. A combination of structural, spectroscopic and computational studies was conducted and provided definitive evidence for bis(arylimidazol-2-ylidene)pyridine radicals in reduced cobalt chemistry. Spin density calculations established that the radicals were localized on the pyridine ring, accounting for the observed reactivity and suggest a wide family of pyridine-based pincers may also be redox active.

show abstract

Section: Resultsmentioning

confidence: 99%

Catalytic Hydrogenation Activity and Electronic Structure Determination of Bis(arylimidazol-2-ylidene)pyridine Cobalt Alkyl and Hydride Complexes

et al. 2013

View full text Add to dashboard Cite

show abstract

“…24 Thermal population of the low-lying triplet excited state accounts for the temperature dependent NMR behavior. In ( iPr PDI)Fe(DMAP) and the ( iPr PDI)CoR class of compounds, the bis(imino)pyridine is best described as redox-active 25,26,27,28,29,30,31 as there is no ambiguity in the oxidation state of either the metal centers or the chelate.…”

Section: Introductionmentioning

confidence: 99%

Electronic Effects in 4-Substituted Bis(imino)pyridines and the Corresponding Reduced Iron Compounds

et al. 2012

View full text Add to dashboard Cite

The electronic structures of the four- and five-coordinate aryl-substituted bis(imino)pyridine iron dinitrogen complexes, (iPrPDI)FeN2 and (iPrPDI)Fe(N2)2 (iPrPDI = 2,6-(2,6-iPr2-C6H3-N=CMe)2C5H3N), have been investigated by a combination of spectroscopic techniques (NMR, Mössbauer, X-ray Absorption and X-ray Emission) and DFT calculations. Homologation of the imine methyl backbone to ethyl or isopropyl groups resulted in the preparation of the new bis(imino)pyridine iron dinitrogen complexes, (iPrRPDI)FeN2 (iPrRPDI = 2,6-(2,6-iPr2-C6H3-N=CR)2C5H3N; R = Et, iPr), that are exclusively four coordinate both in the solid state and in solution. The spectroscopic and computational data establish that the (iPrRPDI)FeN2 compounds are intermediate spin ferrous derivatives (SFe = 1) antiferromagnetically coupled to bis(imino)pyridine triplet diradical dianions (SPDI = 1). While this ground state description is identical to that previously reported for (iPrPDI)Fe(DMAP) (DMAP = 4-N,N-dimethylaminopyridine) and other four-coordinate iron compounds with principally σ-donating ligands, the d-orbital energetics determine the degree of coupling of the metal-chelate magnetic orbitals resulting in different NMR spectroscopic behavior. For (iPrRPDI)Fe(DMAP) and related compounds, this coupling is strong and results in temperature independent paramagnetism where a triplet excited state mixes with the singlet ground state via spin orbit coupling. In the (iPrRPDI)FeN2 family, one of the iron SOMOs is essentially dz2 in character resulting in poor overlap with the magnetic orbitals of the chelate, leading to thermal population of the triplet state and hence temperature dependent NMR behavior. The electronic structures of (iPrRPDI)FeN2 and (iPrPDI)Fe(DMAP) differ from (iPrPDI)Fe(N2)2, a highly covalent molecule with a redox non-innocent chelate that is best described as a resonance hybrid between iron(0) and iron(II) canonical forms as originally proposed in 2004.

show abstract

“…4) (Toma & ChavezGil 1997). This species exhibits the characteristic MLCT bands of the iron(II)-polyimine and Ru(II)-bipy chromophores at 584 and 486 nm, respectively, and an emission band at 614 nm ascribed to the decay of the lowest 3 MLCT state in the [Ru(bipy) 2 Cl] + group.…”

Section: Polymetallic Bipyrazine and Polyimine Complexesmentioning

confidence: 95%

Supramolecular chemistry and technology

Toma

2000

An. Acad. Bras. Ciênc.

Self Cite

View full text Add to dashboard Cite

Supramolecular chemistry deals with the association of several chemical species, in an organized way and according to well defined purposes. Based on a molecular engineering approach, supramolecular structures can be designed from pre-formed building blocks, providing a promising route from chemistry to molecular nanotechnology. New supramolecular systems have been assembled in our laboratory with the use of bridging unities such as tetrapyridylporphyrins, porphyrazines and polypyrazines, connecting transition metal complexes and clusters. These systems display a very exciting electrochemical and catalytic behavior, and interact with DNA, generating 1 O 2 and leading to efficient oxidative clivage for photodynamic terapy applications. Molecular interfaces have been developed, exhibiting photocurrent response in the presence of visible-UV light, and rectifying properties in the presence of electroactive species. Successful applications of the supramolecular species in chemical and bio-sensors have been developed.

show abstract

Synthesis and characterization of a polymetallic supermolecule containing four ruthenium(II)-bipyridine complexes attached to an iron(II) polyimine center

Cited by 38 publications

References 21 publications

Catalytic Hydrogenation Activity and Electronic Structure Determination of Bis(arylimidazol-2-ylidene)pyridine Cobalt Alkyl and Hydride Complexes

Catalytic Hydrogenation Activity and Electronic Structure Determination of Bis(arylimidazol-2-ylidene)pyridine Cobalt Alkyl and Hydride Complexes

Electronic Effects in 4-Substituted Bis(imino)pyridines and the Corresponding Reduced Iron Compounds

Supramolecular chemistry and technology

Contact Info

Product

Resources

About